Previous attempts have been made in the prior art to produce a fire-resisting glass window containing a liquid medium between fire resistant glass sheets. French application No. 76/09227, filed Mar. 30, 1976, by the applicant, proposed to produce such a fire resistant glass window by introducing into the free space an aqueous gel. The aqueous gel contained mineral salts able to produce an insulating foam under the effect of heat radiation. Thus, the gel polymerizes when exposed to fire, thereby producing an insulating foam. The addition of mineral salts, however, quickly resulted in a drop in the optical qualities of the fire resistant glass window, i.e., especially a drop in the transparency.
Another defect of multiple panes of fire resistant glass windows containing an aqueous gel between the glass sheets is the gel mobility or fluidity when the glass is subject to fire's extreme temperatures. In the case of fire, it has been found that the gel has a tendency to collapse, thereby forming relatively large aerated zones. Often the collapse continues until one large aerated zone is formed. Meanwhile, the panes exposed to the fire deform, break, and finally fall away from the door.
Additional considerations arise when a multiple pane fire resistant window is subject to repeated shock as in its role as the main element of a fireproof door. Door mounted aqueous film-multiple pane units are subject to bubbling after a certain number of jarring shocks. The bubbles can possess relatively large volumes and are mobile along the inside surfaces of the glass sheets. Thus, the aqueous film is detached from a glass sheet's inside face. The combination of the above traits results in an aqueous gel-multiple pane door which exhibits poor fireproofing properties.
The present invention discloses a fire resistant glass window which remedies the above inadequacies by significantly reducing the gel mobility via the addition of an adherence agent to the glass sheets' inside faces. The adherence agent's addition results in an aqueous gel which will not bubble when subjected to repeated jarring shocks and, therefore, exhibits improved fireproofing properties.